Bradforth, Stephen E. - University of Southern California

个人简介

Ph.D., 1992, University of California, Berkeley B.A., 1987, Cambridge University

研究领域

Physical Chemistry

The research in the Bradforth group centers on understanding the ultrafast dynamics of chemical reactions in solution and in complex condensed phase systems. The common strand in our experiments is to explore the coupling of the dynamics of the nuclei (e.g. vibrations, bond formation/breaking and solvent motion) to a given non-adiabatic electronic process. The time scales for these non-adiabatic processes are on the order of 100 fs; likewise the timescales of nuclear motions are 10 fs - 1 ps. In a condensed environment, this allows only a short time window to explore the system evolution and catch the newly-formed products before complete relaxation. Femtosecond spectroscopy is therefore the appropriate experimental technique to elucidate the dynamics. Most small molecule photochemistry that is well characterized in the gas phase takes place at wavelengths shorter than 350 nm. Our group follows reactions of such molecules when embedded in a liquid. However, the ultraviolet is traditionally a difficult area for ultrashort pulse generation. We have recently harnessed developments in hollow core fiber technology to achieve breakthrough tunable deep UV pulses of ~ 25 fs. When combined with fully dispersed spectral probing we carry out solution photochemistry experiments exploiting this unprecedented time resolution. Experimental projects using ultrafast spectroscopy in the Bradforth group include (i) probing the primary pathways for electron ionization and detachment in liquid water (ii) investigating chemistry initiated by ejection of an ultrafast electron, (iii) the influence of solvent on bond dissociation dynamics and on rotational relaxation initiated by photodissociation, (iv) determining pathways of energy migration of an electronic excitation through an organized architecture of chromophores such as DNA. Strong connection with current theory is emphasized in all projects. In addition, we are engaged in several collaborative projects with theoreticians in the areas of electronic structure and quantum dynamics of solutes in bulk liquids.

近期论文

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"Nuclear uptake of ultrasmall gold-doxorubicin conjugates imaged by fluorescence lifetime imaging microscopy (FLIM) and electron microscopy", X. Zhang, S. Shastry, S. E. Bradforth, and J. L. Nadeau, Nanoscale, in press (2015). link "Symmetry-Breaking Charge Transfer of Visible Light Absorbing Systems: Zinc Dipyrrins", C. Trinh, K. Kirlikovali, S. Das, M. E. Ener, H. B. Gray, P. Djurovich, S. E. Bradforth, and M. E. Thompson, Journal of Physical Chemistry C 118, 21834-45 (2014). link "Oxidation half-reaction of aqueous nucleosides and nucleotides via photoelectron spectroscopy augmented by ab initio calculations", C. A. Schroeder, E. Pluhařová, R. Seidel, W. P. Schroeder, M. Faubel, P. Slavíček, B. Winter, P. Jungwirth, and S. E. Bradforth, Journal of the American Chemical Society, in press (2014). link "On The Possibility of Combining Radiotherapy and Photodynamic Therapy", K. A. Kudinov, D. Cooper, P. Tyagi, C. Hill, J. Ha, J. Nadeau, and S. Bradforth, CLEO: 2014 Postdeadline Paper Digest, STh5C.1 (2014). link "Quantifying Charge Recombination in Solar Cells Based on Donor–Acceptor P3HT Analogues", S. Das, P. P. Khlyabich, B. Burkhart, S. T. Roberts, E. Couderc, B. C. Thompson, and S. E. Bradforth, Journal of Physical Chemistry C 118, 6650-60 (2014). link "Ultrafast electron transfer from low band gap conjugated polymer to quantum dots in hybrid photovoltaic materials", E. Couderc, M. J. Greaney, W. Thornbury, R. L. Brutchey, and S. E. Bradforth, Proceedings of SPIE-The International Society for Optical Engineering 9165, 91650P-P-7 (2014). link "Deconvoluting Contributions of Photo-Excited Species in Polymer- Quantum Dot Hybrid Photovoltaic Materials", E. Couderc, M. J. Greaney, W. Thornbury, R. L. Brutchey, and S. E. Bradforth, Journal of Photonics for Energy, in press (2014). link "Photoluminescence of cerium fluoride and cerium-doped lanthanum fluoride nanoparticles and investigation of energy transfer to photosensitizer molecules", D. R. Cooper, K. Kudinov, P. Tyagi, C. K. Hill, S. E. Bradforth, and J. L. Nadeau, Physical Chemistry Chemical Physics : PCCP 16, 12441-53 (2014). link "Chalcogenol Ligand Toolbox for CdSe Nanocrystals and Their Influence on Exciton Relaxation Pathways", J. J. Buckley, E. Couderc, M. J. Greaney, J. Munteanu, C. T. Riche, S. E. Bradforth, and R. L. Brutchey, ACS Nano 8, 2512-21 (2014). link "Direct Spectroscopic Evidence of Ultrafast Electron Transfer from a Low Band Gap Polymer to CdSe Quantum Dots in Hybrid Photovoltaic Thin Films", E. Couderc, M. J. Greaney, R. L. Brutchey, and S. E. Bradforth, Journal of the American Chemical Society 135, 18418-26 (2013). link "Fused Porphyrin–Single-Walled Carbon Nanotube Hybrids: Efficient Formation and Photophysical Characterization", Q. Zhong, V. V. Diev, S. T. Roberts, P. D. Antunez, R. L. Brutchey, S. E. Bradforth, and M. E. Thompson, ACS Nano 7, 3466-75 (2013). link "Exploring the Energy Disposal Immediately After Bond-Breaking in Solution: The Wavelength-Dependent Excited State Dissociation Pathways of para-Methylthiophenol", Y. Zhang, T. A. A. Oliver, S. Das, A. Roy, M. N. R. Ashfold, and S. E. Bradforth, Journal of Physical Chemistry A 117, 12125–37 (2013). link "Photoelectron Angular Distributions from Liquid Water: Effects of Electron Scattering", S. Thürmer, R. Seidel, M. Faubel, W. Eberhardt, J. C. Hemminger, S. E. Bradforth, and B. Winter, Physical Review Letters 111, 173005 (2013). link "On the nature and origin of dicationic, charge-separated species formed in liquid water on X-ray irradiation.", S. Thürmer, M. Oncak, N. Ottosson, R. Seidel, U. Hergenhahn, S. E. Bradforth, P. Slavícek, and B. Winter, Nature Chemistry 5, 590-6 (2013). link "Photon quenching in InGaN quantum well light emitting devices", R. Sarkissian, S. T. Roberts, T.-W. Yeh, S. Das, S. E. Bradforth, J. OBrien, and P. Daniel Dapkus, Applied Physics Letters 103, 041123 (2013). link "Unexpectedly Small Effect of the DNA Environment on Vertical Ionization Energies of Aqueous Nucleobases", E. Pluhařová, C. Schroeder, R. Seidel, S. E. Bradforth, B. Winter, M. Faubel, P. Slavícek, and P. Jungwirth, Journal of Physical Chemistry Letters 4, 3766-9 (2013). link "Emission of Macrocyclic and Linear Poly(2-vinylnaphthalene): Observation of Two Excimer Populations in Macrocycles", G. G. Nossarev, J. Johnson, S. E. Bradforth, and T. E. Hogen-Esch, Journal of Physical Chemistry C 117, 10244-56 (2013). link "Aqueous Colloidal Acene Nanoparticles: A New Platform for Studying Singlet Fission", J. N. Mastron, S. T. Roberts, R. E. McAnally, M. E. Thompson, and S. E. Bradforth, Journal of Physical Chemistry B 117, 15519-26 (2013). link "Comparing molecular photofragmentation dynamics in the gas and liquid phases", S. J. Harris, D. Murdock, Y. Zhang, T. A. A. Oliver, M. P. Grubb, A. J. Orr-Ewing, G. M. Greetham, I. P. Clark, M. Towrie, S. E. Bradforth et al., Physical Chemistry Chemical Physics 15, 6567 (2013). link "Differential effects of β-mercaptoethanol on CdSe/ZnS and InP/ZnS quantum dots", M. Georgin, L. Carlini, D. Cooper, S. E. Bradforth, and J. L. Nadeau, Physical Chemistry Chemical Physics 15, 10418 (2013). link